The present invention relates to a braking pressure regulating device, in particular an anti-lock control device, traction slip control device for hydraulic brake systems of automotive vehicles, comprising a master cylinder with at least one working piston, (push rod piston and/or floating piston) and at least one working chamber, a supply reservoir for pressure fluid, a pressure modulator for the variation of the hydraulic pressure in the wheel cylinders of the wheel brakes during the braking pressure control mode, the said pressure modulator including inlet and outlet valves for the wheel cylinders, an electronic control unit for the control of the valves of the modulator, at least one motor-driven pump for generating a hydraulic pressure, the working chamber of the master cylinder being applied by pump pressure in the braking pressure control mode and the working piston of the master cylinder being movable in the direction of its initial position caused by the pump pressure, a regulating valve being provided in at least one working piston which, in the braking pressure control mode, regulates the pressure fluid flow in the hydraulic fluid cycle that is composed of pump, working chamber of the master cylinder, supply reservoir (pressure fluid flow regulation).
Braking pressure regulating devices, in particular in the form of anti-lock systems, are used in the motor vehicle industry in increasingly large numbers. In specific categories of these anti-lock systems, hydraulic pumps are used for generating an auxiliary pressure during the control mode.
A like anti-lock device has become known from e.g. German published patent application DE-OS 36 41 712.2.
This application describes a valve for a brake system with slip control, with a pedal-operated, preferably auxiliary-force assisted braking pressure generator, with a master cylinder to which the wheel brakes are connected via main brake lines, with hydraulic auxiliary-pressure pumps as well as with wheel sensors and electronic circuits for determining the wheel rotational behaviour and for generating electric braking pressure control signals permitting to control electromagnetically actuatable pressure-fluid inlet valves and outlet valves inserted for slip control into the pressure fluid lines, with the pistons of the master cylinder comprising valves which, in the brake's release position, open pressure-fluid connections between the pressure fluid supply reservoir and the pressure chambers and which close these pressure-fluid connections in the braking position.
The special characteristics of this device reside in that valves arranged in the pistons of the master cylinder comprise in each case a valve member longitudinally slidable in a recess and cooperating in each case with an opening member, e.g. a tappet, in such a fashion that the tappet moves the valve member into its opened position when the respective piston is in its release position, with the tappet taking support on a stationary pivot, cross member or bolt, and with each recess being closed on the side facing the pressure chamber by means of a bowl portion which serves as a support of the respective valve-closure spring.
In braking pressure regulating devices of the described known type, the pump pressure causes the brake pedal to return to its initial position during the control mode. This is not desirable in many events. Due to this shift-back, the operating comfort for the driver is impaired.
It is an object of the present invention to devise a braking pressure regulating device wherein the brake pedal is not slid back into its initial position during the control mode.
Further, it should also be possible to achieve several positions of the brake pedal in front of its initial position. Besides, it is principally desired to improve the pedal feeling during the control mode.
These improvements are to be accomplished by means as simple as possible, and the solution of the object is to be cost-efficient.
There should be need for only few and fail-safe component parts.
The need for additional sensors should be obviated. It should not be necessary to alter the brake power booster.